Display device

Abstract

There is disposed a TFT for detecting characteristic having the same characteristic as a pixel TFT disposed at a pixel. The TFT for detecting characteristic detects a gate on voltage for driving the pixel TFT. The TFT for detecting characteristic is driven so as to agree with the pixel TFT in a period of the on state. This provides a display device that is capable of driving the pixel TFT at its optimum driving voltage with a simple circuit configuration, even when the characteristic of the pixel TFT is subjected to temperature change, aged change, and individual variations.

1 . A display device comprising: 
 a plurality of pixels that are arranged in a matrix-shape on a substrate and are respectively provided with a pixel TFT; and    at least one TFT for detecting characteristic that is formed on said substrate so as to have the same characteristic as said pixel TFT, and detects an on voltage or an off voltage for driving said pixel TFT,    said at least one TFT for detecting characteristic being driven so as to agree with said pixel TFT in a period of an on state.    
   
   
       2 . The display device according to  claim 1  wherein, 
 said at least one TFT for detecting characteristic has a control terminal and a current input terminal that are connected to each other; and    said on voltage or said off voltage is detected by applying a bias current to a connecting part between said control terminal and said current input terminal.    
   
   
       3 . The display device according to  claim 1 , further comprising: 
 a gate voltage control circuit that controls a gate voltage of said at least one TFT for detecting characteristic, wherein,    said at least one TFT for detecting characteristic detects said on voltage or said off voltage by control of said gate voltage that enables flow of a predetermined current identical with a current required for said pixel TFT.    
   
   
       4 . The display device according to  claim 1  wherein said at least one TFT for detecting characteristic is driven by a gate driving circuit that drives said pixel TFT.  
   
   
       5 . The display device according to  claim 1 , further comprising: 
 a common voltage generating circuit that commonly applies a common voltage to said plurality of pixels, wherein,    said common voltage is changed in response to said on voltage or said off voltage.    
   
   
       6 . The display device according to  claim 1  wherein said at least one TFT for detecting characteristic contains a plurality of TFTs for detecting characteristic, said plurality of TFTs for detecting characteristic being connected in parallel.  
   
   
       7 . The display device according to  claim 1  wherein, 
 said at least one TFT for detecting characteristic contains a plurality of TFTs for detecting characteristic;    a voltage dividing part is further provided that divides an output between said plurality of TFTs for detecting characteristic; and    said pixel TFT is driven by an on voltage or an off voltage that is divided by said voltage dividing part.    
   
   
       8 . The display device according to  claim 1  wherein, 
 said at least one TFT for detecting characteristic contains a plurality of TFTs for detecting characteristic; and    said plurality of TFTs for detecting characteristic are arranged at an end of a gate wiring of said pixel TFT arranged in a plurality of rows.